1 // Allocators -*- C++ -*- 2 3 // Copyright (C) 2001-2022 Free Software Foundation, Inc. 4 // 5 // This file is part of the GNU ISO C++ Library. This library is free 6 // software; you can redistribute it and/or modify it under the 7 // terms of the GNU General Public License as published by the 8 // Free Software Foundation; either version 3, or (at your option) 9 // any later version. 10 11 // This library is distributed in the hope that it will be useful, 12 // but WITHOUT ANY WARRANTY; without even the implied warranty of 13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 // GNU General Public License for more details. 15 16 // Under Section 7 of GPL version 3, you are granted additional 17 // permissions described in the GCC Runtime Library Exception, version 18 // 3.1, as published by the Free Software Foundation. 19 20 // You should have received a copy of the GNU General Public License and 21 // a copy of the GCC Runtime Library Exception along with this program; 22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 23 // <http://www.gnu.org/licenses/>. 24 25 /* 26 * Copyright (c) 1996-1997 27 * Silicon Graphics Computer Systems, Inc. 28 * 29 * Permission to use, copy, modify, distribute and sell this software 30 * and its documentation for any purpose is hereby granted without fee, 31 * provided that the above copyright notice appear in all copies and 32 * that both that copyright notice and this permission notice appear 33 * in supporting documentation. Silicon Graphics makes no 34 * representations about the suitability of this software for any 35 * purpose. It is provided "as is" without express or implied warranty. 36 */ 37 38 /** @file bits/allocator.h 39 * This is an internal header file, included by other library headers. 40 * Do not attempt to use it directly. @headername{memory} 41 */ 42 43 #ifndef _ALLOCATOR_H 44 #define _ALLOCATOR_H 1 45 46 #include <bits/c++allocator.h> // Define the base class to std::allocator. 47 #include <bits/memoryfwd.h> 48 #if __cplusplus >= 201103L 49 #include <type_traits> 50 #endif 51 52 #define __cpp_lib_incomplete_container_elements 201505L 53 54 namespace std _GLIBCXX_VISIBILITY(default) 55 { 56 _GLIBCXX_BEGIN_NAMESPACE_VERSION 57 58 /** 59 * @addtogroup allocators 60 * @{ 61 */ 62 63 // Since C++20 the primary template should be used for allocator<void>, 64 // but then it would have a non-trivial default ctor and dtor for C++20, 65 // but trivial for C++98-17, which would be an ABI incompatibiliy between 66 // different standard dialects. So C++20 still uses the allocator<void> 67 // explicit specialization, with the historical ABI properties, but with 68 // the same members that are present in the primary template. 69 70 /** std::allocator<void> specialization. 71 * 72 * @headerfile memory 73 */ 74 template<> 75 class allocator<void> 76 { 77 public: 78 typedef void value_type; 79 typedef size_t size_type; 80 typedef ptrdiff_t difference_type; 81 82 #if __cplusplus <= 201703L 83 // These were removed for C++20, allocator_traits does the right thing. 84 typedef void* pointer; 85 typedef const void* const_pointer; 86 87 template<typename _Tp1> 88 struct rebind 89 { typedef allocator<_Tp1> other; }; 90 #endif 91 92 #if __cplusplus >= 201103L 93 // _GLIBCXX_RESOLVE_LIB_DEFECTS 94 // 2103. std::allocator propagate_on_container_move_assignment 95 using propagate_on_container_move_assignment = true_type; 96 97 using is_always_equal 98 _GLIBCXX20_DEPRECATED_SUGGEST("std::allocator_traits::is_always_equal") 99 = true_type; 100 101 #if __cplusplus >= 202002L 102 // As noted above, these members are present for C++20 to provide the 103 // same API as the primary template, but still trivial as in pre-C++20. 104 allocator() = default; 105 ~allocator() = default; 106 107 template<typename _Up> 108 constexpr 109 allocator(const allocator<_Up>&) noexcept { } 110 111 // No allocate member because it's ill-formed by LWG 3307. 112 // No deallocate member because it would be undefined to call it 113 // with any pointer which wasn't obtained from allocate. 114 #endif // C++20 115 #endif // C++11 116 }; 117 118 /** 119 * @brief The @a standard allocator, as per C++03 [20.4.1]. 120 * 121 * See https://gcc.gnu.org/onlinedocs/libstdc++/manual/memory.html#std.util.memory.allocator 122 * for further details. 123 * 124 * @tparam _Tp Type of allocated object. 125 * 126 * @headerfile memory 127 */ 128 template<typename _Tp> 129 class allocator : public __allocator_base<_Tp> 130 { 131 public: 132 typedef _Tp value_type; 133 typedef size_t size_type; 134 typedef ptrdiff_t difference_type; 135 136 #if __cplusplus <= 201703L 137 // These were removed for C++20. 138 typedef _Tp* pointer; 139 typedef const _Tp* const_pointer; 140 typedef _Tp& reference; 141 typedef const _Tp& const_reference; 142 143 template<typename _Tp1> 144 struct rebind 145 { typedef allocator<_Tp1> other; }; 146 #endif 147 148 #if __cplusplus >= 201103L 149 // _GLIBCXX_RESOLVE_LIB_DEFECTS 150 // 2103. std::allocator propagate_on_container_move_assignment 151 using propagate_on_container_move_assignment = true_type; 152 153 using is_always_equal 154 _GLIBCXX20_DEPRECATED_SUGGEST("std::allocator_traits::is_always_equal") 155 = true_type; 156 #endif 157 158 // _GLIBCXX_RESOLVE_LIB_DEFECTS 159 // 3035. std::allocator's constructors should be constexpr 160 _GLIBCXX20_CONSTEXPR 161 allocator() _GLIBCXX_NOTHROW { } 162 163 _GLIBCXX20_CONSTEXPR 164 allocator(const allocator& __a) _GLIBCXX_NOTHROW 165 : __allocator_base<_Tp>(__a) { } 166 167 #if __cplusplus >= 201103L 168 // Avoid implicit deprecation. 169 allocator& operator=(const allocator&) = default; 170 #endif 171 172 template<typename _Tp1> 173 _GLIBCXX20_CONSTEXPR 174 allocator(const allocator<_Tp1>&) _GLIBCXX_NOTHROW { } 175 176 #if __cpp_constexpr_dynamic_alloc 177 constexpr 178 #endif 179 ~allocator() _GLIBCXX_NOTHROW { } 180 181 #if __cplusplus > 201703L 182 [[nodiscard,__gnu__::__always_inline__]] 183 constexpr _Tp* 184 allocate(size_t __n) 185 { 186 if (std::__is_constant_evaluated()) 187 { 188 if (__builtin_mul_overflow(__n, sizeof(_Tp), &__n)) 189 std::__throw_bad_array_new_length(); 190 return static_cast<_Tp*>(::operator new(__n)); 191 } 192 193 return __allocator_base<_Tp>::allocate(__n, 0); 194 } 195 196 [[__gnu__::__always_inline__]] 197 constexpr void 198 deallocate(_Tp* __p, size_t __n) 199 { 200 if (std::__is_constant_evaluated()) 201 { 202 ::operator delete(__p); 203 return; 204 } 205 __allocator_base<_Tp>::deallocate(__p, __n); 206 } 207 #endif // C++20 208 209 friend _GLIBCXX20_CONSTEXPR bool 210 operator==(const allocator&, const allocator&) _GLIBCXX_NOTHROW 211 { return true; } 212 213 #if __cpp_impl_three_way_comparison < 201907L 214 friend _GLIBCXX20_CONSTEXPR bool 215 operator!=(const allocator&, const allocator&) _GLIBCXX_NOTHROW 216 { return false; } 217 #endif 218 219 // Inherit everything else. 220 }; 221 222 /** Equality comparison for std::allocator objects 223 * 224 * @return true, for all std::allocator objects. 225 * @relates std::allocator 226 */ 227 template<typename _T1, typename _T2> 228 inline _GLIBCXX20_CONSTEXPR bool 229 operator==(const allocator<_T1>&, const allocator<_T2>&) 230 _GLIBCXX_NOTHROW 231 { return true; } 232 233 #if __cpp_impl_three_way_comparison < 201907L 234 template<typename _T1, typename _T2> 235 inline _GLIBCXX20_CONSTEXPR bool 236 operator!=(const allocator<_T1>&, const allocator<_T2>&) 237 _GLIBCXX_NOTHROW 238 { return false; } 239 #endif 240 241 /// @cond undocumented 242 243 // Invalid allocator<cv T> partial specializations. 244 // allocator_traits::rebind_alloc can be used to form a valid allocator type. 245 template<typename _Tp> 246 class allocator<const _Tp> 247 { 248 public: 249 typedef _Tp value_type; 250 template<typename _Up> allocator(const allocator<_Up>&) { } 251 }; 252 253 template<typename _Tp> 254 class allocator<volatile _Tp> 255 { 256 public: 257 typedef _Tp value_type; 258 template<typename _Up> allocator(const allocator<_Up>&) { } 259 }; 260 261 template<typename _Tp> 262 class allocator<const volatile _Tp> 263 { 264 public: 265 typedef _Tp value_type; 266 template<typename _Up> allocator(const allocator<_Up>&) { } 267 }; 268 269 /// @} group allocator 270 271 // Inhibit implicit instantiations for required instantiations, 272 // which are defined via explicit instantiations elsewhere. 273 #if _GLIBCXX_EXTERN_TEMPLATE 274 extern template class allocator<char>; 275 extern template class allocator<wchar_t>; 276 #endif 277 278 // Undefine. 279 #undef __allocator_base 280 281 // To implement Option 3 of DR 431. 282 template<typename _Alloc, bool = __is_empty(_Alloc)> 283 struct __alloc_swap 284 { static void _S_do_it(_Alloc&, _Alloc&) _GLIBCXX_NOEXCEPT { } }; 285 286 template<typename _Alloc> 287 struct __alloc_swap<_Alloc, false> 288 { 289 static void 290 _S_do_it(_Alloc& __one, _Alloc& __two) _GLIBCXX_NOEXCEPT 291 { 292 // Precondition: swappable allocators. 293 if (__one != __two) 294 swap(__one, __two); 295 } 296 }; 297 298 // Optimize for stateless allocators. 299 template<typename _Alloc, bool = __is_empty(_Alloc)> 300 struct __alloc_neq 301 { 302 static bool 303 _S_do_it(const _Alloc&, const _Alloc&) 304 { return false; } 305 }; 306 307 template<typename _Alloc> 308 struct __alloc_neq<_Alloc, false> 309 { 310 static bool 311 _S_do_it(const _Alloc& __one, const _Alloc& __two) 312 { return __one != __two; } 313 }; 314 315 #if __cplusplus >= 201103L 316 template<typename _Tp, bool 317 = __or_<is_copy_constructible<typename _Tp::value_type>, 318 is_nothrow_move_constructible<typename _Tp::value_type>>::value> 319 struct __shrink_to_fit_aux 320 { static bool _S_do_it(_Tp&) noexcept { return false; } }; 321 322 template<typename _Tp> 323 struct __shrink_to_fit_aux<_Tp, true> 324 { 325 _GLIBCXX20_CONSTEXPR 326 static bool 327 _S_do_it(_Tp& __c) noexcept 328 { 329 #if __cpp_exceptions 330 try 331 { 332 _Tp(__make_move_if_noexcept_iterator(__c.begin()), 333 __make_move_if_noexcept_iterator(__c.end()), 334 __c.get_allocator()).swap(__c); 335 return true; 336 } 337 catch(...) 338 { return false; } 339 #else 340 return false; 341 #endif 342 } 343 }; 344 #endif 345 /// @endcond 346 347 _GLIBCXX_END_NAMESPACE_VERSION 348 } // namespace std 349 350 #endif 351